本文转载至机器学习初学者（ID：ai-start-com）
作者：黄海广博士
1. 安装说明
2. 使用说明
- 比如画出分类评级指标的ROC曲线的完整代码：
from sklearn.datasets import load_digits
from sklearn.model_selection import train_test_split
from sklearn.naive_bayes import GaussianNB
X, y = load_digits(return_X_y=True)
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.33)
nb = GaussianNB()
nb.fit(X_train, y_train)
predicted_probas = nb.predict_proba(X_test)
# The magic happens here
import matplotlib.pyplot as plt
import scikitplot as skplt
skplt.metrics.plot_roc(y_test, predicted_probas)
plt.show()
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- P-R曲线就是精确率precision vs 召回率recall 曲线，以recall作为横坐标轴，precision作为纵坐标轴。首先解释一下精确率和召回率。
import matplotlib.pyplot as plt
from sklearn.naive_bayes import GaussianNB
from sklearn.datasets import load_digits as load_data
import scikitplot as skplt
# Load dataset
X, y = load_data(return_X_y=True)
# Create classifier instance then fit
nb = GaussianNB()
nb.fit(X,y)
# Get predicted probabilities
y_probas = nb.predict_proba(X)
skplt.metrics.plot_precision_recall_curve(y, y_probas, cmap='nipy_spectral')
plt.show()
-
- 混淆矩阵是分类的重要评价标准，下面代码是用随机森林对鸢尾花数据集进行分类，分类结果画一个归一化的混淆矩阵。
from sklearn.ensemble import RandomForestClassifier
from sklearn.datasets import load_digits as load_data
from sklearn.model_selection import cross_val_predict
import matplotlib.pyplot as plt
import scikitplot as skplt
X, y = load_data(return_X_y=True)
# Create an instance of the RandomForestClassifier
classifier = RandomForestClassifier()
# Perform predictions
predictions = cross_val_predict(classifier, X, y)
plot = skplt.metrics.plot_confusion_matrix(y, predictions, normalize=True)
plt.show()
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